When James Martin was eight, he predicted he’d be a head chef by 30, have his own restaurant by 35 and a Ferrari by 40. Instead, he’d achieved them all by the age of 24.

Now that he’s 40, with TV shows including BBC1’s Saturday Kitchen, best-selling books, restaurants, a delicatessen, cookware range and a campaign to revamp hospital food, James is rapidly on his way to becoming as prolific as Jamie Oliver.

But success is not all he and Oliver have in common – both are dyslexic, something James credits with giving him the drive to succeed.

As he travels the US with a new series on baking, Martin explains how he built a £5m fortune despite being unable to read

‘I think it’s because you’re proving yourself all the time. It’s not financial. It’s about proving to yourself that you can do it because when you were younger you were five to ten years behind everybody else at school. I’ve always had to fight for everything. Now I’m of the belief that if I don’t do something, somebody is going to beat me to it so that keeps me going. I still feel like I’m fighting now. I will never think I have it all and sit back.’

So rather than relaxing and enjoying the estimated £5 million fortune he’s amassed, James has made another TV series, James Martin’s United Cakes Of America, in which he bakes authentic desserts from each state along the East coast of the US.

‘I thought it was just doughnuts and pretzels in America but baking is massive over there – every family in America bakes,’ he explains. ‘By comparison, the British fascination with baking is relatively new.’

James’s own fascination with baking started long ago, when he was growing up on a Yorkshire pig farm watching his mother, grandmother and aunt cook. James also spent time washing pots at Castle Howard, the stately home where Brideshead Revisited was filmed and where his father worked as estate manager.

‘I’m a workaholic. I was brought up as a farmer’s son – it wasn’t the good life, it was a hard life,’ he recalls. ‘I wanted somewhere to warm up. We had a nice Aga and kitchen, so I loved cooking. It was the one thing I could do well. I didn’t realise I was dyslexic and I was failing all my exams, so I used to get depressed. But cooking was a release.’

At 12 he was almost thrown out of school cookery classes because he dared to serve up flambéed chicken with mangetout instead of fairy cakes like the rest of the class. ‘I could do dishes better than my cookery teacher but because I couldn’t write the recipes down, I failed.’

James’s own fascination with baking started long ago, when he was growing up on a Yorkshire pig farm watching his mother, grandmother and aunt cook

Undeterred, James went to what was one of the country’s top catering colleges at the time, Scarborough Technical College, where he won student of the year three years running and was offered a job by Antony Worrall Thompson, a judge for his final exams, at London’s One Ninety Queen’s Gate.

‘I came to London with £50 in my pocket and a dream,’ smiles James. ‘The hours were ridiculous – from 7am to 3am – but I never moaned. I’d sleep in the kitchen and use the potwash water spout as a shower. Marco Pierre White told me that to be a chef you have to be half an artist and half a donkey.’

It paid off because, by the age of 22, James was appointed head chef at the first Hotel du Vin in Winchester. A television producer, who was among the starry clientele, gave Martin her card, insisting, ‘I can make you a star.’ She sent a chauffeur-driven car to take him to a meeting in London because he couldn’t afford the train fare on his £11,000 salary.

Soon he was cooking on Channel 4’s Big Breakfast then Ready Steady Cook, before taking over Saturday Kitchen from Worrall Thompson in 2006 and doubling the ratings with a new format.

Now he barely spends time at his Hampshire home – where the Ferrari lives, along with a few other classic cars – and, despite being a bit of a pin-up, is unmarried.

But he has a girlfriend and a string of glamorous exes, including James Bond film producer Barbara Broccoli, 52, daughter of the first Bond producer, Cubby Broccoli, with whom he had a four-and-a-half-year relationship. Broccoli ‘won’ James in a charity auction in 2001, paying £18,000 for him to cook a meal for her.

Resolutely unstarry, James’s best mates are a plumber, builder and mechanic and after finishing Saturday Kitchen, he goes home to be with his clumber spaniel, Fudge, and watch TV. This unassuming manner is probably what has made Saturday Kitchen a success as his celebrity guests feel able to relax. But it’s not always easy.

In his new show viewers will see him put a British spin on classic American recipes, adding Yorkshire parkin spices to New York cheesecake and making the world’s first cream tea whoopee pie

‘I’m not an actor so you can see it in my face if I find the celebrities hard work,’ says James. ‘I have people like Jerry Springer on and I think, “What are you doing here on a Saturday morning? And what am I doing here?” I’m just a Yorkshire cook who’s so dyslexic I can’t read the autocue.

‘I’ve never read a book because I can’t. So I’m under pressure with the massive chunk of script in the first part of the show. When that’s out of the way, I can relax.’

In contrast, filming his new series was a joy because there was no script, just lots of opportunities for James to get out there, meet people and, of course, cook.

Viewers will see him put a British spin on classic American recipes, adding Yorkshire parkin spices to New York cheesecake and making the world’s first cream tea whoopee pie.

‘You never stop learning with food nor do I want to stop learning as I’ll be overtaken,’ says James. ‘I don’t want that to happen because to have people eat food that I’ve cooked makes me happier than anything else.’

James Martin’s United Cakes Of America, Sunday-Wednesday, 8pm, Good Food.